I think you are confusing fasting and abstinence.
The only two days fasting is required are Ash Wednesday and Good Friday. Abstaining from meat is also an obligation on these days as it is for all Fridays in Lent.
No. The United States Conference of Catholic Bishops has determined that Friday abstinence from meat is an obligation but that other penances may be substituted for the other Fridays of the year. The Canadian Conference of Catholic Bishops has determined that the prerogative of substituting another penance for Friday abstinence is extended to all the Fridays of the year except Good Friday.
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Statement Regarding Fast and Abstinence
The CCCB decrees that the days of fast and abstinence in Canada are Ash Wednesday and Good Friday.
Fridays are days of abstinence, but Catholics can substitute special acts of charity or piety on these days. Accordingly, our CCCB urges us to take up the challenge of meaningful penance as expressed in fast and abstinence. They call us to become more mindful of our loving Creator and Redeemer. They ask us to be generous and faithful in our practices of penance. It is never a question of undermining one’s health. On the other hand, we should be aware of those sensible acts of penance that can actually improve our bodily health.
In a practical vein, our Bishops propose that all who are well enough, and of the prescribed age, begin now to observe abstinence on every Friday of the year that is not a major feast (e.g. Christmas Day) and to fast and abstain on Ash Wednesday and Good Friday. Individuals may wish to do more penance, but as a community let the Church at least observe the recommended days of abstinence and the two days of both fast and abstinence.
ABSTINENCE:
Will mean not to eat meat or some other favorite food and a practice of moderation in all food and drink on a given day.
FASTING:
Can vary from person to person. Some people will be able to make a total fast; eating only bread and drinking only water; others will adopt a vegetarian diet on a day of fast; others still will take only one complete meal. Each person needs to decide according to his or her ability, work and condition. But no one form is better than another, so long as it is done generously and with a good motive.
The Bishops invite all to consider every Friday of the year, and especially the season of Lent, as opportune times to praise God and ask for his blessings, to be attentive to almsgiving and other works of charity, and to strive to grow in compassion. To visit the sick, to support the needy and to offer assistance to third world countries would be practical ways of expressing genuine love for those others dear to the Lord.
People are asked to begin the practice of abstinence after their 14th birthday; fasting would obligate those who have celebrated their 18th birthday and for a period up to their 59th birthday, although all, no matter what their age, should be taught the meaning of penance. (Canon 1252)*
(from the Canadian Conference of Catholic Bishops 2003)
romancatholic.kingston.on.ca/Statement%20re%20fast%20and%20abstinence.pdf